US2344298A - Resistor device - Google Patents

Description

March 14, 1944- c. B. GREEN 4,

RESISTOR DEVICE Filed Jan. 21, 1942 INVENTOR c. B. GREEN Wm M A TTORNEY Patentedllar. 14, 1944 um'rsn srA'rssPArsN'r orr cs assss'roa DIVICI mlesLGreemWestMgaNJsa-igaasto Ne'YoskJi. 1., annotation oiNewYosk Application January :1. 1842, Serial No. 427.588

(!. sis-1s) iClaim.

Thisinvention relatestoresistordevicesand more particularly to constnictional features thereof.

In resistors of the type known as thermlstors, i. e.. those having a relatively hish absolute value oi resistance-temperature coeiilcient, control of thermal characteristics and conditions is of particular importance. For example, if the thermistor is used to measure temperature, care must be taken that the thermistor current does not have an appreciable heating efiect on the thermistor or that compensation for this eilect be made. On the other hand, it one is interested in the resistance variation due to current heating,,account must be taken of ambient temperature. Oneway oi doingthisisto employheating or cooling means in the immediate vicinity of the thermistor to maintain some predetermined ambient temperature. The present invention involves certain structural. features that combine to provide the necessary means for adequate ambient temperature control in thermistor devices An object 0! this invention is to construct a small bead type thermistor having ambient temperature control means that are accurate and relatively rugged.

One feature of the invention lies in structure that maintains accurate spacing between the heater and the thermistor with which it is associated.

Another feature of this invention resides in a coil type heater adapted to maintain its proper configuration under operating conditions.

Other and i'urther objects and features of this invention will be understood more iully and clearly from the following description oi illustrative embodiments thereoi taken in connection with the appended drawing in which:

Fig. l is a perspective view of an illustrative form oi the invention in which the elements are enclosed in a suitable envelope;

Fig. 2 is an enlarged view of the device withthereto. l'orexample, ilmaybeabeadoisemiconductive material having a high resistancetemperature coeillcient such as a heat treated mixture of a suitable combination of two or more of the oxides oi manganese, nickel, cobalt and copper. The leads II and I! may be fine wires of platinum or platinum-iridium alloy or the like embedded in the head.

The thermistor element it may be provided with more than two leads as illustrated in Figs. 4 and 5. In Fig. 4 the leads ll, 4!, and ii, 52, are respectively part of the same corductors. The tour leads may also consist of four separate conductors or three may be used as leads 4|, 5i and ii in 1'18. 5.

The heater II, as illustrated in Figs. 1, 2 and 3, may be a coil 01' fine wire impregnated with a ceramic cement. A suitable wire is one comprising an alloy of nickel and chromium. The coil may have two end leads I4 and II respectively and a center tap ll. As shown in Fig. 3, the end leads and center tap are radially spaced at approximately degrees for a. purpose to be later described.

The coil structure it may be made by winding the proper number of turns of wire on a mandrel and then impregnating the resulting coil with a suitable ceramic cement. A convenient way of applying the cement is to spray it on the coil, coating each turn and filling the spaces between turns. The cement may then be dried and baked. This cement may be made of an aggregate such as aluminum oxide and a binder comprising one or more of the glass forming compounds.

Instead of a coil, the heater may be, as shown in Figs. 6 and 'l, a cylinder or tube 4i 0! resistance material having end connectors ii and it and a center connector 48. Although a three point heater suspension has been found particularly suitable more than three supports may be used on either form of heater as the particular requirements demand.

A plurality of supports 2|. 2|, 22,13 and 24, four of which are in the illustrated modification, secured in the press II of the enclosing envelope It, are maintained in spaced relation by member 21. The envelope 2! may be of glass and member 21 may be a glass bead. The supports should be of an electrically conductive material that can be properly sealed in the glass. An alloy wire oi suitable proportions of copper, nickel and iron, may be used.

As indicated in the drawing. the s pports 20 to 30, inclusive, which are embedded in the bead 21 bent into suitable configur tions to support several elements. The upper ends of sup- II, II, and 28 are respectively adjacent the ,oente andhottomoicoil ll. Thesupports that their upp portions are equally EEQEE N 2! and 28 res ii heater 4! is employed.

in the modification illustrated, support I! does doctors to an external circuit. Obviously, it an electrical connection to tap II or II is desired, support I! maybeextendedtotheoutside oithe envelope. 1! the heater is to be supported at more than three points. additional supports must be provided and the spacing arrangement made accordingly. For example. with a four point heater support, the supports would be spaced at 90 degree intervals around the heater axis.

Attached to the top of support 2|, which in the modification illustrated extends above the other supports, is a spring SI to which is secured one lead ii of the thermistor element". The other thermistor lead I! is secured to a bent over portion II of the support N. The spring II and portion ll are oriented so that the thermistor leads lie substantially along the axis of coil ii. The leads ii and II are sosecured to SI and Ii that the thermistor II is supported substantially at the center the heater ll 01''". Th spring I is held under slight fiexure so that the leads ii and I! are under tension. The leads may be weldedtollandli. Inthecaseoispring "and lead ll,bothareordinarilysofine thatanenclesing sleeve I! of metal is employed to obtain a suitable joint. The wire ii is wrapp d around the spring 30 adjacent its end, the sleeve 32 applied and a spot weld made through the sleeve; lead and spring. Final adjustment of thermistor location and lead tension may be made by slightly bending the portion ll oi the support 24 to the proper position. a v

I! a three or four lead thermistor element is employed, the support structure is modified accordingly. For example. with a thermistor such as the one shown in Fig. 4, there would be two resilient members like the spring SI and two adjustable support portions like i I Obviousiy,various support combinations may be provided to suit particular requirements without departing from the basic structural ieatures set iorth in the modification illustrated and particularly described.

The member ll mounted on support N by an auxiliarysupportliisaholderiorthegetterused in envelope evacuation;

The constructional ieatures or the device at this invention combine to produce a resistor device that is relatively rugged and capable oi maintaining proper interelement spacing under rather severe conditions of use. Since the regulatory functions required of this type oi thermistor must be accurately performed, the novel structure herein disclosed is at considerable importance in actual circuit applications.

Although this invention has been disclosed by means oi a particular illustrative embodiment thereof, it is tobe understood that modifications maybemsdethereinwithinthespiritandsccpe o! the appended claim.

What is claimed is:

In a resistor deviceincluding a small resistor unit having a pair oi leads projecting oppositely therefrom, an orificed, radiant heater, and an envelope for enclosing the wit and heater, means for supporting the unit and heater within said envelope comprising a plurality of conductors seaiabiy mounted in spaced relation through a portion or said envelope, said heater comprising a plurality of turns of wire wound in a cylindrical coil with a center tap and and connections. said coil impregnated with an insulating material rendering it relatively rigid, the axial length or said coil exceeding the length or the unit in the direction of the projecting leads, the heater having its end connections and center tap secured respectively to three of said conductors spaced approximately degrees apart around the axis of said coil, one 01. the leads of said resistor \mit being connected to a portion or another of the supporting conductors. said portion lying approximately at right angles to the axis of the coil, and the other of said leads connected to a bowed spring member having one end in line with said axis and the other secured to still another oi. the support conductors, said right angle conductor portion and spring member being adjusted to apply a slight tension to the leads and to susp nd the resistor unit within the orifice of said heater approximately at its center.

13. cam.

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